The present invention relates to automated material handling systems, and particularly those of the type employed in warehouses for retrieving articles from vertically arranged stacks. Such devices are often referred to as "stackers", and are typically rail guided and equipped with traction motive means to provide self-propelled movement between the warehouse stacks. Typically, mobile stackers of the aforesaid type employ a vertical mast mounted on the rail-guided self-propelled carriage, and have an extensible shuttle movably disposed on the mast for retrieving objects from the stacks.
Automated storage and retrieval systems of the above-described type are usually customized installations in a particular warehouse building, and require accurate location and laying of the guiding rails and alignment of the carriage and mast with respect to the stacks for enabling remote control of the self-propelled carriage and shuttle. The systems are typically erected and assembled piece by piece in the particular warehouse to be serviced. The mobile stacker, and particularly the mast assembly are usually formed of steel plate or I-beam construction requiring welding and matched drilling of holes for bolting. These structures are not only costly to assemble, by are quite heavy and thus possess a substantial inertia, which creates problems for braking of the carriage during movement to a desired position adjacent the stacks.
It has therefore been desired to provide a mobile stacker for automated storage and retrieval systems which is light in weight and employs maximum use of prefabricated components, and which may be assembled on site in a warehouse with a minimum of assembly operations at installation.